Currently, various radio communication systems exist such as 2nd generation radio communication systems such as PDC and GSM, 3rd generation radio communication systems such as W-CDMA, and PHS and wireless LAN. As a technique for supporting a plurality of radio communication systems using a single radio apparatus, software defined radio exists that varies between functions by updating of software (programming data).
When switching between radio communication systems (which generally means handover between radio communication systems or the case of updating programming data, but it is herein assumed that handover includes the case of only updating programming data), a conventional software defined radio apparatus downloads software to support a communication system of a handover destination switching from a communication system used in current communications of a communication apparatus, and then, reconfigures a communication apparatus that supports a radio communication system of the handover destination using the downloaded data.
With respect to switching of radio communication systems, there is a method for implementing the switching by reprogramming (reconfiguring) a reconfigurable device (for example, see Japanese Laid-Open Patent Publication H11-220413). Further, it is considered providing a download dedicated channel to implement fast download (for example, see Japanese Laid-Open Patent Publication 2000-324043).
Currently, in a mobile communication terminal, it is demanded to switch from a communication system of current communications to another communication system at high speed, and concurrently, it is desired to improve the user capacity of the entire system. From these viewpoints, in the constitution as disclosed in Patent Document 1, a call is suspended or disconnected during download, and it is not possible to perform fast handover between radio communication systems. Further, as disclosed in Patent Document 2, when a download dedicated channel is provided to download programming data, there are possibilities that spectral efficiency deteriorates and the user capacity of the entire system decreases.
When data of a radio communication system with a large amount (hereinafter, referred to as “large-scale”) of programming data is downloaded during communication in a narrowband radio communication system with low transmission rates, retransmission is apt to occur and it takes enormous time to complete the download. In particular, retransmission occurs remarkably in poor radio signal propagation circumstances.
Further, when individual mobile communication terminals are operated to perform fast download in a wideband radio communication system with high transmission rates, there arise problems that the spectral efficiency deteriorates and the user capacity of the entire system decreases.
Furthermore, when a reconfigurable device such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array) is used in the mobile radio baseband signal processing, it is possible to support any operation such as, for example, FFT (Fast Fourier Transform), correlator, and FEC (Forward Error Correction), flexibility is thus high, and development time is shortened. However, the circuit scale and power consumption tends to increase in PLD and FPGA.
Meanwhile, when custom ASIC is used in the mobile radio baseband signal processing, it is possible to suppress the circuit scale and power consumption because of dedicated circuitry, but flexibility is low because application is limited to, for example, FFT when FFT is used. Further, its development time is long.
As described above, in conventional apparatuses, when a communication apparatus downloads programming data of a radio communication system and switches details of the system to the downloaded programming data, there exist such problems that an amount of programming data is large, download time is long, and it takes much time to switch between systems.